I read both Catcher and On The Road at 17 for the first time, back to back, and while I think my age definitely played a part in the way those works affected me, I'm not sure if it would be different now, at 33, since both books still hold great meaning for me, particularly Catcher.
I think that Catcher hits so many nails on so many heads that is is hard for it not to resonate into adulthood, provided you don't fall off the cliff, reach for the ring, etc etc...And even though my life has changed dramatically since being 17, that is all external. Inwardly I am exactly the same person, so maybe that's why I still love the book.
I think mainly, as Jimmy Snerp said, a lot of the Kerouac appreciation regards nostalgia for how you felt ORIGINALLY reading him, as a kid or a young adult.
I have only discovered Bukowski less than a year ago, and I think it's good that I found him now, at this age. It's like a whole world opening up. At 17, I'm not sure I would have gotten the work woes, the female woes that are rife in his writing...I'd have understood the contempt for people and the lack of enthusiasm for normal daily life, but I think everything else would have been over my head, then.
I recently read Queer, by Burroughs, who is a writer I've aways been aware of and interested in but only just now actually delved into. I thought Queer was very good, but lacking something...it has sensitivity and the narrative was pretty good but I don't know, he can't seem to NOT come across as a very cold, almost alien kind of person. But the self-loathing and unrequited desire that jumps out from every page is just profound; it definitely gave a new depth to way I looked at Burroughs who up til then I just thought was all cerebral and detached.
I know his other books are not all so straightforward and human...
